Projectile



INVENTORS HENRYE DUNLAP AT ORNEY United States Patent O This invention relates to sabot projectiles of the type comprising a subcaliber core and substantially full caliber sabot means mounted on the core for supporting and center-ing the core in a gun barrel and releasable from the core under centrifugal force when the projectile emerges from a gun barrel. More particularly, the invention relates to a novel projectile of the type described in which the full caliber sabot means is threaded on the core in such a manner that resistance of the core to fracturing on impact is not substantially affected.

Sabot projectiles have been made heretofore in Which the sabot is in the form of an elongated sleeve mounted on a subcaliber core. It has been proposed to secure the sleeve on the core by means of interengaging threads on these members, as disclosed in a copending application of H. F. Dunlap and C. E. Hablutzel, Serial No. 543,007, filed June 30, 1944 now Patent No. 2,968,246. However, it has been found that when the subcaliber core is provided on its cylindrical surface with conventional threads, the resulting sharp reentrant angles cause high stress concentrations in the heat treating of the projectile, and on impact of the projectile with a target, such high stresses are liable to cause fracture or cracking of the projectile core.

One object of the present invention, therefore, resides in the provision of a sabot projectile having a sabot sleeve threaded on a subcaliber core in such a manner that high stress concentrations in the core, due to the threads, are avoided.

Another object of the invention is to provide a sabot projectile comprising a subcaliber core carrying a full caliber discardable sabot, 'and a connection between the core and sabot comprising an annular female portion on the core including vgrooves extending around the outside of the core and having bottoms which are rounded in a plane parallel to the core axis, and an internal annular male portion on the sabot including protrusions extending around the inside of the support and having crests Which are rounded in a plane parallel to the core axis, the protrusions being fitted closely in the groove.

Still another object of the invention is to provide a sabot projectile comprising a subcaliber core having an external thread course in which the root is rounded and the crest is pointed in a plane parallel to the core axis, and a full caliber, sleeve-like, discardable sabot for receiving the core and provided with an internal thread having a crest which is rounded and a root Ywhich is pointed in a plane parallel to the core axis, the sabot thread being screwed into the course on the core.

These and other objects of the invention may be better understood by reference to the accompanying drawing, in which FIG. 1 is a side elevational view, partly in section, of a sabot projectile made in accordance with the invention, and

FIG. 2 is an enlarged detail view, partly in section, of the projectile core shown in FIG. 1.

Referring to the drawing, the projectile as shown comprises a subcaliber core 10 made of steel and having an ogive lita. An elongated initially one-piece sleeve-like member 11 is mounted on the cylindrical portion of the core and extends continuously from the ogive 10a to a point adjacent the base of the core. The sleeve 11, which may be made of metal or a light-weight material, such as 2,996,011 Patented Aug. 15, 1901 2 ,j a plastic or fiber, is of substantially full caliber dimension and is adapted to support and center the core in a gun barrel, the front end portion of the sleeve serving in effect as a bourrelet and the rear end portion of the sleeve serving as a sabot. Mounted on the sabot portion of the sleeve 11 is a turning band 12 which maybe made of annealed copper, the band being press-fitted, threaded or otherwise mounted on the sleeve. The band 12 has an external diameter somewhat greater than that of the sleeve 11, so that the band is adapted to be engraved by the rifling in the gun barrel to impart rotation to the core through the sleeve.

The sleeve 11 is counectedto the core 10 by meansl of a thread course 13 on the cylindrical surface of the core, the thread mating with a complementary thread 14 on the inner surface of the sleeve. As shown, the thread 13 has a root 1311 which is fully rounded in a plane parallel to the axis of the core, in other words crosswise of the direction of the course, while the crest 13b of the thread which constitutes a continuous spiral edge deriving its substantial sharpness from the adjacent upcurves of the root is also pointed in a plane parallel to the core aXis. The thread 14 on the inner cylindrical surface of sleeve 11 is adapted to fit closely in the thread 13` and has a crest which is rounded in a plane parallel to the core axis so that the crest conforms to the configuration of the root 13a of the thread on the core. Also, the thread 14 on the sleeve has a root which is pointed in a plane parallel to the core axis, so that the root conforms closely to the configuration of the crest 13b of the core thread.

In assembling the projectile, the sleeve 11 is screwed on the core 10 and tightened against the front end of the thread course on the core. The threads 13 and 14 are in such a direction that the torque imparted to the sleeve 11 by turning band 12 acts to tighten the sleeve against the front end of the thread course 13. When the projectile is fired from the gun, the powder pressure acts upon the -base of the core and also upon the rear end of the sleeve 11 and turning band 12. As a projectile moves through the gun barrel, the sleeve 11 is held together on the core 10 by the confining effect of the gun barrel; but when the projectile emerges from the gun muzzle, the sleeve 11 breaks apart under the action of centrifugal force incident to the high speed rotation of the projectile, this release being insured in practice by cutting two or more radial slots in said sleeve 11. Accordingly, the core 10 may proceed along its trajectory without the aerodynamic drag which would otherwise be imposed upon it 'by the sleeve 11.

By employing threads of the form described, to connect the sleeve to the core, the usual sharp reentrant angles of conventional threads are eliminated. This is an important feature of the present invention because in the manufacture of high velocity projectiles of the character described, it is necessary to subject the core 10 to a heat treating process so that it will have the desired qualities for armor piercing. The sharp reentrant angles of conventional threads Would lead to high stress concentrations upon heat treating of the core 10 and upon impact of the projectile core with an armored target, with the result that the projectile core might fracture or crack. However, with the new construction, the only sharp reentrant angles are in the sleeve 14 which is not subjected to the heat treating process and is discarded from the core as soon as the projectile emerges from the gun muzzle.

By reason of the rounded root 13:1 of the core thread, the core may be heat treated in the usual manner after formation of the threads, without cracking or fracturing of the threaded portion of the core, and the latter is not appreciably affected by impact against a target. It has `lprojectile to provide a screw thread, a unitary full caliber 10 support of tubular shape on said core, said support being of frangible material whereby it will break apart during 'the 'flight of 'the projectile under the action of centrifugal force incident to rotation of the projectile, a spiral rib having a semicircular rounded crest formed on the inner 15 4 wall of said support and extending the length thereof to provide a screw thread to mate with the screw thread on said core, the radius of the Semicircular cross section of said groove being equal to the radius of the semicircular 5 cross section of said rib.

References Cited in the file of this patent UNITED STATES PATENTS 657,297 Sheffield Sept. 4, 1900 2,021,685 Fornaci Nov. 19, 11935 2,119,994 Love June 7, 1.938 2,152,681 Caminez Apr. 4, 1939 VFOREIGN PATENTS 131,034 Great Britain Aug. 21, 1919 

